鄂尔多斯盆地东部奥陶系古岩溶型碳酸盐岩致密储层特征、形成机理与天然气富集潜力

doi:10.11743/ogg20180406

摘要/Abstract

摘要： 目前鄂尔多斯盆地东部古岩溶型碳酸盐岩储层的研究相对薄弱，因此开展奥陶系古岩溶型储层形成机理与天然气富集潜力研究可为天然气储量的发现和开发前景评价奠定基础。通过对鄂尔多斯盆地东部奥陶系岩溶储层特征、形成控制因素、天然气富集主控因素与富集潜力的评价分析，认为盆地东部碳酸盐岩风化壳储层较为发育，气源供给充足，源-运-储配置关系良好，具备天然气规模富集的条件。鄂尔多斯盆地盆地东部岩溶储层总体表现为低孔与致密的特征，将孔隙度为3%、渗透率为0.05×10^-3 μm²确定为储层物性下限标准；将孔隙直径为30 μm、喉道直径为5 μm界定为储层孔、喉尺度下限标准。有利沉积微岩相、有效岩溶作用和综合成岩作用等共同影响储层形成，半充填型硬石膏结核云岩为最重要的储层类型。研究认为天然气富集主控因素包括：①有效储层发育是天然气富集的基础物质条件；②良好的源-运-储配置关系是天然气富集的关键。总体而言，盆地东部下古碳酸盐岩岩溶储层具备较大的勘探开发潜力。

关键词: 物性下限, 天然气富集, 古岩溶储层, 奥陶系, 鄂尔多斯盆地东部

Abstract: The Ordovician palaeokarst carbonate reservoirs in the eastern Ordos Basin are poorly understood at present.Thus it will be fundamental for discovering gas reserves and evaluating its developmental prospects to analyze the formation mechanism of the palaeokarst reservoirs and the gas accumulation potentials of the Ordovician carbonates.We elaborated the reservoir characteristics,controlling factors for the reservoir formation,major controlling factors of gas accumulation and storage capacity of the Ordovician carbonates in the study area.The conclusion is that in the eastern Ordos Basin,the weathered crust reservoirs of carbonates are well developed,gas source is sufficient and the timing of source,migration and reservoir is good,so the area is favorable for large-scale gas accumulation. In terms of the reservoir characte-rization,it is featured by low porosity and low permeability as a whole,with the porosity of 3% and permeability of 0.05×10^-3 μm² being regarded as the lower limit of physical property for effective reservoir,and with the pore diameter of 30 μm and throat diameter of 5 μm regarded as the lower limit of reservoir pore-throat sizes.The generation of high-quality carbonate paleokarst reservoir is mainly effected by favorable sedimentary microfacies,effective karstification,and integrated diagenesi,etc.Dolomite with anhydrite concretions of half-filling type is the most important high-quality reservoirs.The controlling factors for gas accumulation are summarized as follows:① the development of high-quality reservoirs lays a substantial basis for gas accumulation;② the favorable timing of source,migration and reservoir is the key.In general,the Lower Paleozoic carbonate karst reservoirs in the eastern Ordos Basin are of great potential for exploration.

Key words: lower limit of physical properties for effective reservoirs, gas accumulation, palaeokarst reservoir, Ordovician, eastern Ordos Basin

中图分类号:

TE122.2

王国亭,程立华,孟德伟,等. 鄂尔多斯盆地东部奥陶系古岩溶型碳酸盐岩致密储层特征、形成机理与天然气富集潜力[J]. 石油与天然气地质, 2018, 39(4): 685-695. doi: 10.11743/ogg20180406 Wang Guoting,Cheng Lihua,Meng Dewei,et al. Characterization and formation of the Ordovician tight paleokarst carbonates in the eastern Ordos Basin and its gas accumulation[J]. Oil & Gas Geology, 2018, 39(4): 685-695. doi: 10.11743/ogg20180406

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